Recent years have seen rapid advances in servicing of communication traffic by optical signals in the field of information and telecommunications, and there has so far been developed a fiber-optic network, such as the backbone, metropolitan, and access systems, over a relatively long distance at least several km. In order to process massive amounts of data travelling over a shorter distance such as rack-to-rack (in a range of several to several hundreds of m), or a distance (in a range of several to several tens of cm) in a transmission device without delay in the future, use of a light signal is considered effective, and a progress is being made in utilization of optical communication techniques for transmission between LSIs, or between an LSI and a backplane, within an information processing equipment such as a router, server, and so forth.
As for adoption of optical interconnection between information devices/within an information device, with a transmission device such as, for example, a router/a switch, a high-frequency signal transmitted from outside such as Ethernet using an optical fiber is inputted to a line card. Further, one sheet of backplane is made up of several sheets of the line cards, and input signals to the line cards are further collected by a switch card through the backplane to be processed by LSIs inside the switch card before being outputted to the line cards through the backplane again. With a transmission device as it is, signals of at least 300 Gbps from the respective line cards converge on the switch card through the backplane at present. For transmission of the signals via electrical interconnects as they are, the signals need be divided into portions, each on the order of 1 to 3 Gbps, so that at least 100 lengths of interconnects will be required in consideration of a propagation loss.
Further, such high-frequency paths need to have a pre-emphasis/equalizer, and countermeasures against reflection, or cross talk between interconnects. As further progress is made in larger capacity of a system from now on, the transmission device will come to process information in terms of at least Tbps, whereupon problems such as the number of lengths of interconnects, and countermeasures against cross talk, and so forth will be increasingly serious to the conventional electrical interconnects. In contrast, if an optical fiber is adopted for a signal transmission path between boards within the device that is, from the line card→ the backplane→ the switch card, and further, for a signal transmission path between chips within a board, this will enable a high-frequency signal of at least 10 Gbps to be propagated with a small loss, so that it is possible to make do with fewer lengths of interconnects, and the countermeasures described as above are no longer required for the high-frequency signal, which is therefore promising. In order to implement such a high-speed optical interconnection circuit, and to apply the same between the devices/within the device, there will be the need for an optical module circuit excellent in respect of performance, miniaturization, integration, and component-mountable property, that can be manufactured by an inexpensive manufacturing means.
What are considered important upon construction of a light signal transmission structure include a coupling part between a photonic device (an optical element) and an optical signal transmission line such as an optical waveguide, an optical fiber, and so forth. When light from a laser diode is caused to propagate to an optical interconnect, or light propagated from an optical signal transmission line is caused to fall on a photo diode, positioning of the optical element and the optical signal transmission line need be implemented with high precision in order to effect sufficiently efficient optical coupling. Meanwhile, in consideration of mass-productivity and practicality, LSIs for use in an optical coupler, and the information device are preferably removable•replaceable with ease
For example, in JP-A-2006-133763, for coupling between the optical element and the optical signal transmission line, a structure is adopted, whereby positioning of the optical element and the optical signal transmission line can be implemented by use of guide pins, thereby effecting mounting of the optical element, and LSIs with the use of socket pins. By so doing, it has become possible to implement the positioning of the optical element and the optical signal transmission line with relative ease, and LSIs are removable with ease as mounting thereof is carried pout with the use of the socket pins.